Field of the Invention
The present invention relates to a color conversion substrate for a light-emitting diode (LED) and a method of fabricating the same. More particularly, the present invention relates to a color conversion substrate for an LED and a method of fabricating the same able to form a hermetic seal, thereby entirely protecting a quantum dot (QD) accommodated in the color conversion substrate from the external environment.
Description of Related Art
A light-emitting diode (LED) is a semiconductor device formed of a compound such as gallium arsenide (GaAs) to emit light when an electrical current is applied thereto. The LED uses a p-n junction of a semiconductor into which minority carriers, such as electrons or holes, are injected, such that light is generated by the recombination of the minority carriers.
The characteristics of LEDs include low power consumption, a relatively long lifespan, the ability to be mounted in cramped spaces, and resistance to vibrations. In addition, LEDs are used in display devices and in backlight units of display devices. Recently, studies into applying LEDs to general illumination devices have been undertaken. In addition to monochromatic LEDs, such as red, blue, or green LEDs, white LEDs have come into the market. In particular, a sharp increase in demand for white LEDs is expected, since white LEDs can be applied to vehicles and lighting apparatuses.
In the field of LED technology, white light is commonly generated using two major methods. The first method to generate white light includes disposing monochromatic LEDs, such as red, green, and blue LEDs, adjacently to each other such that light emitted by the monochromatic LEDs having various colors is mixed. However, color tones may change depending on the environment in which such devices are used, since individual monochromatic LEDs have different thermal or temporal characteristics. In particular, color stains may occur, making it difficult to uniformly mix different colors of light. The second method to generate white light includes applying a fluorescent material to an LED and mixing part of initial light emitted by the LED and secondary light wavelength-converted by the fluorescent material. For example, a fluorescent material generating yellowish-green or yellow light may be used as a light excitation source on a blue LED, whereby white light can be produced by mixing blue light emitted by the blue LED and yellowish-green or yellow light excited by the fluorescent material. At present, the method of realizing white light using a blue LED and a fluorescent material is generally used.
Currently, a quantum dot (QD) generating strong light having a narrower wavelength than that of a typical fluorescent material is used as a color conversion material. In general, a QD-LED backlight generates white light by irradiating a yellow QD with blue light emitted by a blue LED, and supplies the white light as backlight to a liquid crystal display (LCD). LCDs using such a QD-LED backlight has high potential as new displays, since the characteristics of these LCDs include superior color reproduction unlike those using a traditional backlight using LEDs only, ability to realize full color comparable to that of LEDs, and lower fabrication costs and higher productivity than LED TVs.
In the related art, a method of fabricating such a QD-LED includes: forming a QD sheet by mixing a QD with polymer; and subsequently coating the QD sheet with a plurality of barrier layers in order to protect the sheet surface from outside moisture or the like and maintain the lifespan. However, this related-art method is problematic in that fabrication costs are expensive due to the barrier layers having to be applied several times, and most of all, this method fails to entirely protect the QD from the external environment.
In addition, another method used in related art includes: etching a glass surface to a certain depth; inputting a QD into the etched portion of the glass surface; covering the resultant structure with a cover glass; applying low melting point glass on the peripheries; sintering the applied low melting point glass; and sealing the resultant structure using a laser beam. However, the etching process causes fabrication costs to be expensive. In particular, it is difficult to use a thin glass plate.
The information disclosed in the Background of the Invention section is only provided for better understanding of the background of the invention and should not be taken as an acknowledgment or any form of suggestion that this information forms prior art that would already be known to a person skilled in the art.